Stationary wedge expandable interbody device

Abstract

An intervertebral implant includes a chassis and endplates movable relative to the chassis. The endplates are each movable between a contracted position, wherein the endplates are nearer to a central axis defined relative to the chassis, and an expanded position, wherein the endplates are farther from the central axis. The chassis includes at least one wedge that, in turn, includes surfaces along which the endplates travel in transition between the contracted and expanded positions. The wedge remains stationary relative to the central axis throughout transitions between the contracted and expanded positions.

The inventio claimed is: 
     
         1 . An intervertebral implant comprising:
 a chassis including a wedge;   an endplate connected to the chassis and movable relative to the chassis along a surface of the wedge between a contracted position and an expanded position, the expanded position being farther from a central axis defined relative to the chassis than the contracted position, with the wedge remaining at a constant position along the central axis in both the expanded position and contracted position; and   a collar translatable along the central axis relative to the wedge to drive movement of the endplate relative to the chassis along the surface of the wedge between the contracted and expanded positions, the collar being connected to the endplate so as to permit the endplate and the collar to translate relative to one another in a direction orthogonal to the central axis but restrict the endplate and the collar from translating relative to one another along a direction parallel to the central axis.   
     
     
         2 . The implant of  claim 1 , comprising a threaded shaft in threaded driving engagement with the endplate, and connected to the chassis such that the shaft extends along and is rotatable about the central axis. 
     
     
         3 . The implant of  claim 2 , wherein the endplate is a first endplate and the implant further comprises a second endplate with which the threaded shaft is in threaded driving engagement such that rotation of the shaft about the central axis drives the first endplate and second endplate in a same direction along the central axis. 
     
     
         4 . The implant of  claim 3 , wherein the second endplate is connected to the chassis and movable relative to the chassis along another surface of the wedge between a contracted position and an expanded position, the expanded position of the second endplate being farther from the central axis than the contracted position of the second endplate. 
     
     
         5 . The implant of  claim 3 , wherein the collar is internally threaded so as to be threadingly engaged with the shaft, the collar being connected to the first endplate and second endplate to provide the threaded driving engagement of the shaft with the first endplate and second endplate. 
     
     
         6 . The implant of  claim 5 , wherein:
 the wedge is a first wedge;   the collar is a first collar threaded onto a first threaded portion of the shaft;   the chassis further includes a second wedge; and   the implant further includes a third endplate and fourth endplate and a second collar;   the third endplate and the fourth endplate each being connected to the chassis and movable relative to the chassis along a respective surface of the wedge between a respective contracted position and a respective expanded position, the respective expanded positions being farther from the central axis than the respective contracted positions; and   the second collar being threaded onto a second threaded portion of the shaft, translatable relative to the second wedge, and connected to the third endplate and fourth endplate to provide threaded driving engagement of the shaft with the third endplate and the fourth endplate.   
     
     
         7 . The implant of  claim 6 , wherein the first threaded portion is threaded in an opposite direction from the second threaded portion. 
     
     
         8 . The implant of  claim 2 , wherein the collar is internally threaded so as to be threadingly engaged with the shaft the collar being connected to the endplate to provide the threaded driving engagement of the shaft with the endplate. 
     
     
         9 . The implant of  claim 8 , wherein the endplate can translate relative to the collar farther in a direction perpendicular to the central axis than in a direction parallel to the central axis. 
     
     
         10 . The implant of  claim 1 , wherein the endplate includes a track extending perpendicular to the central axis and the collar includes a peg received in the track. 
     
     
         11 . The implant of  claim 10 , wherein the implant is configured for the track and peg to travel along the central axis along with the collar. 
     
     
         12 . An intervertebral implant comprising:
 a chassis including a first wedge and a second wedge spaced apart from one another along a central axis; and   a pair of first endplates and a pair of second endplates each connected to the chassis and movable relative to the chassis between a contracted configuration of the implant and an expanded configuration of the implant, wherein each of the first endplates is movable along a respective surface of the first wedge and each of the second endplates is movable along a respective surface of the second wedge, such that each of the first endplates and each of the second endplates are farther from the central axis in the expanded configuration than in the contracted configuration, and the first endplates move away from the second endplates along the central axis when moving from the contracted configuration to the expanded configuration,   wherein the first and second wedges are each located at a constant position along the central axis in both the contracted configuration and the expanded configuration.   
     
     
         13 . The implant of  claim 12 , comprising a first collar to which the first endplates are connected and a second collar to which the second endplates are connected, the first and second collars being simultaneously translatable along the central axis relative to the chassis. 
     
     
         14 . The implant of  claim 12 , wherein the surfaces of the first wedge, along which the first endplates are movable, mirrors the surfaces of the second wedge, along which the second endplates are movable. 
     
     
         15 . The implant of  claim 12 , wherein each of the first endplates is connected to the respective surface of the first wedge along which the first endplates may move and each of the second endplates is connected to the respective surface of the second wedge along which the second endplates may move such that each of the first and second endplates are constrained to moving only along the respective surface. 
     
     
         16 . The implant of  claim 12 , wherein the pair of first endplates are a distal pair of endplates and the pair of second endplates are a proximal pair of endplates, and wherein the distal pair of endplates are at more distal positions and the proximal pair of endplates are at more proximal positions in the expanded configuration than in the contracted configuration. 
     
     
         17 . The implant of  claim 12 , wherein the chassis includes two rods extending parallel to the central axis to hold the first and second wedges at their respective fixed positions. 
     
     
         18 . The implant of  claim 12 , wherein the pair of first endplates are translatable together along the central axis while moving away from one another on opposing sides of the first wedge, and wherein the pair of second endplates are translatable together along the central axis while moving away from one another on opposing sides of the second wedge. 
     
     
         19 . An intervertebral implant comprising:
 a chassis including a first wedge and a second wedge spaced apart from one another along a central axis;   a threaded shaft connected to the chassis such that the shaft extends along and is rotatable about the central axis; and   a first endplate and a second endplate each connected to the threaded shaft such that, upon rotation of the threaded shaft about the central axis, the first and second endplates are movable relative to the chassis along a respective surface of a respective one of the first and second wedges between a contracted configuration of the implant and an expanded configuration of the implant, the first and second endplates being farther from the threaded shaft in the expanded configuration than in the contracted configuration, and the first endplate moves away from the second endplate along the central axis when moving from the contracted configuration to the expanded configuration,   wherein the first and second wedges are each located at a constant position along the central axis in both the contracted configuration and the expanded configuration.   
     
     
         20 . The implant of  claim 19 , wherein the first endplate and the second endplate are each connected to the threaded shaft via a respective internally threaded collar threadingly engaged with the shaft.